loplugin:externvar (clang-cl)

Change-Id: I638199f1455bead71f0a03f15e4b6f418a0cd0e2

compilerplugins/clang/externvar.cxx

@@ -8,6 +8,7 @@
  */
 
 #include "check.hxx"
+#include "compat.hxx"
 #include "plugin.hxx"
 
 // Find variable declarations at namespace scope that need not have external
@@ -72,6 +73,14 @@ public:
             // not needed and will not be emitted"
             return true;
         }
+        SourceLocation argLoc;
+        if (compat::isMacroArgExpansion(compiler, def->getLocation(), &argLoc)
+            && (Lexer::getImmediateMacroName(
+                    argLoc, compiler.getSourceManager(), compiler.getLangOpts())
+                == "DEFINE_GUID"))
+        {
+            return true;
+        }
         report(
             DiagnosticsEngine::Warning,
             "variable with external linkage not declared in an include file",